Nevado del Ruiz Eruption-1985
The Nevado del Ruiz eruption of 1985 was one of the most destructive eruptions in history. Part of its aftermath was the largest lahar in geological history, bringing the fatality total to over 23,000 people.
The Nevado del Ruiz is located in the northern region of Colombia on the Andes Volcanic Chain. The summit elevation of the Nevado is 5,389 m (17,500 ft).
The Nevado del Ruiz is located in the northern region of Colombia on the Andes Volcanic Chain. The summit elevation of the Nevado is 5,389 m (17,500 ft).
Nevado del Ruiz is an explosive, active, stratovolcano. Stratovolcanos form at a convergent plate margins, and have steep summit slopes and a surprisingly small crater. After nearly a year of minor earthquakes and steam explosions from Nevado del Ruiz, the volcano exploded violently on November 13, 1985. The initial blast began at 3:06 p.m., and two hours later pumice fragments and ash were showering down on Armero. However, the citizens of Amero remained calm. They were placated by reassuring messages from the mayor over radio, and from a local priest over the church public address system. At 9:08 p.m., just as calm was being restored, molten rock began to erupt from the summit crater for the first time (all previous eruptions were steam explosions). The violent ejection of this molten rock generated hot pyroclastic flows and airfall tephra that began to melt the summit ice cap. Unfortunately, a storm obscured the summit area so that most citizens were unaware of the pyroclastic eruption. Meltwater quickly mixed with the erupting pyroclastic fragments to generate a series of hot Lahars. These are one of the most deadly consequences of Nevado del Ruiz during an eruption. As hot pyroclastic flows sweep down the sides of Nevado delRuiz, it causes a rapid melting of snow and ice and creates very large floods that sweep down the volcano and through valleys. As these floods flow more quickly, they pick up loose debris and soil, growing in density and volume to form extremely hot mood flows (lahars). These lahars can be as large as 50 meters thick and travel over 50 km per hour. They destroy everything surrounding them, and are the cause of thousands of deaths and destruction of cities. Many hazards come with a Nevado del Ruiz eruption, all harmful, and many deadly.Traveling at 50 kilometers per hour, the largest of these burst through an upstream damn on the River Lagunillas and reached Armero two hours after the eruption began. Most of the town was swept away or buried in only a few short minutes, killing three quarters of the townspeople.
Lahars are syrupy in substance, in a liquid state while in motion and solid when stopped, very similar to concrete. The Nevado del Ruiz lahar became a worldwide phenomenon due to the death toll it created and the Omayra Sanchez incident.
Lahars are syrupy in substance, in a liquid state while in motion and solid when stopped, very similar to concrete. The Nevado del Ruiz lahar became a worldwide phenomenon due to the death toll it created and the Omayra Sanchez incident.